Pan Pacific Symposium Conference Proceedings


HEAD STACK ASSEMBLY PERCUSSION SWAGE PROCESSING MORPHOLOGIES FOR HARD DISK DRIVE PRODUCTS

Authors: Jeffry S. Bennin and Michael R. Tiller
Company: Hutchinson Technology Inc.
Date Published: 1/26/2010   Conference: Pan Pacific Symposium


Abstract: Hard Disk Drive memory storage products comprise an assortment of mechanical and micro-electronic components and subassemblies attached and combed into a finished product. One such attachment involves a mechanical ball swage interference fit, providing a solid, stable and economical means of integrating the precision head suspension spring to the E-block arm of the Head Stack Assembly. Challenges arise, in optimizing component design and processing to ensure a robust attachment of multiple head suspensions to the arm stack without negatively impacting the attitude of the head as it flies mere nanometers above the rotating disk surface. Operational temperature extremes, high lateral seek and shock loads, dissimilar materials, process rework, cleaning, and chemical compatibility requirements all underscored with a driving necessity to minimize costs, has retained swage attachment as the predominant head suspension attachment process in HDD products for over 20 years.

The approach is not without its compromises, however, as an intricate balance of mechanical stiffness, minimized mass, and complex compressible features are designed into the baseplate component of the suspension assembly to attain both operational performance and processing objectives. Swage processing applies axial loads of 180 – 270N (40 – 60lbf), converted to compressive radial loads within the intricately patterned, ring-shaped boss tower, securely restraining the suspension assembly in a patterned hole in the E-block arm. High axial loads, however, can result in unfavorable deformation of the swage plate flange structure, with the potential to negatively impact head flight attitude. This paper will study the effects of impact or percussion swage processing as a means of transforming the power spectrum input to the system, reducing the axial force applied to the baseplate. Should impulse energy loading alter the static to dynamic friction states at the onset of compression swage, it may be possible significantly reduce the baseplate flange deformation and its associated impacts on flight attitude without deploying prohibitive lubricants, or significant modifications to established tooling and equipment infrastructure. Potential benefits may include future design and process modifications to minimize variation and further reduce feature complexity and resulting cost.

Keywords: Impact, Vibro-Impact, Percussion, Swage, Head Stack Assembly, HSA, Head Gimbal Assembly, HGA, Suspension Assembly, Hard Disk Drive, HDD, Baseplate, Swagebase, Dynamic Mass, Gram Load, Static Friction, Dynamic Friction.



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